Current sources are generally of the voltage-to-current type converters. In such converters the output current is directly proportional to the input voltage. Unless the input voltage is from a highly stable voltage source, the output current will be subject to the variations and fluctuations of the input voltage.
It is important in many operations, such as in resistivity measuring apparatus and systems, to have a source of current that exhibits a constant-current level free of any such variations and fluctuations. Accordingly, it is a specific feature of the present invention to provide for such a constant-current source.